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Historical Background Information: West Clay Properties Page 4 of 7 during the soil over-excavation procedures. The mass of petroleum hydrocarbons residing in soil was determined on the basis of the averaged concentrations of TPH-g in the soil samples collected from the walls and floor of the excavation area during excavation and previous site assessment activities.AGE's calculations estimated that approximately 5.2 lbs or 0.8 gal of gasoline remain in soil at the site. Ground Water Monitoring- Based on analytical results of ground water samples collected during quarterly monitoring and site assessment activities, the most impacted ground water appears to be centered around EW-1 and MW-10. The vertical extent of the contamination plume, as well as the lateral extent east and south of the former UST cluster, is not well defined. CPT INVESTIGATION Between 0l and 04 June 2004,four CPT soil borings(CPT-01 through CPT-04)and 11 individually established soil borings for collection of ground water samples were advanced at the southern UST No. 3 location and the northern UST cluster area. CPT soil borings were advanced at the following locations - ground water samples were collected from dedicated borings at the following intervals: • CPT-01, CPT-02 and associated ground water sampling borings were advanced near the northern boundary of the former UST No. 3 location (Figures 2 and 3) to determine the vertical extent of petroleum hydrocarbon-impacted ground water.CPT-01 and CPT-02 were co-located borings. CPT-01 was advanced to approximately 100 feet bsg; CPT-02 was advanced to approximately 170 feet bsg- CPT-01 was sampled between 77 and 81 feet bsg and between 93.5 and 97.5 feet bsg while later CPT-02 was sampled between 114 and 118 feet bsg and between 137 and 141 feet bsg; • CPT-03 and associated ground water sampling borings were advanced south-southwest of the former UST No. 3 location to determine the down-gradient extent of petroleum hydrocarbon-impacted ground water. CPT-03 was advanced to approximately 210 feet bsg -CPT-03 was sampled between 50 and 54 feet bsg, 74 and 78 feet bsg, 133 and 137 feet bsg and 176 and 180 feet bsg; • CPT-04 and associated ground water sampling borings were advanced north of the former UST cluster excavation (Figures 2 and 4) to determine the vertical extent of petroleum hydrocarbon-impacted ground water at the former UST cluster area. CPT-03 was advanced to approximately 175 feet bsg. • Ground water sampling boring CHB-01 was advanced approximately 70 feet east-northeast of CPT-04 to determine the vertical extent ofpetroleum hydrocarbon-impacted ground water down-gradient of the former UST cluster area-CPT-04 was sampled between 80 and 84 feet bsg and 166 and 170 feet bsg; while - soil boring CHB-01 was sampled between 78 and 82 feet bsg. Advanced GeoEnvironmental,Inc.